Dimerization of 2-methyl-1-pentene



April 20, 1965 T E MPE RAT URE IN DE GREES C.

s. RATAJCZAK ETAL.

DIMERIZATION OF 2-METHYL-1PENTENE Filed Aug. 28, 1961 D ISTILL ATE IN ml INVENTORS sums LAS RATA'JCZ AK ALFRED PARIS United States Patent 3,179,710 DIMERIZATION 0F Z-METHYL-l-PENTENE Stanislas Ratajczak, Marcq-en-Baroeul, and Alfred Paris,

Neuilly-sur-Seiue, France, assignors to Manufactures de Produits Chimiques du Nord Etahlissemeuts Kuhlmann, Paris, France, a corporation of France Filed Aug. 28, 1961, Ser. No. 134,514 Claims priority, application France, Sept. 2, 1960, 837,711 Claims. (Cl. 260--683.15)

This invention relates to the selective dimerization of Z-methyl-l-pentene.

It is known that propylene, when placed in proper conditions of temperature and pressure in the presence of alkyl-aluniinium dimerizes to yield 2-methyl-l-pentene. One of the essential features of the method is the very high yield of Z-methyl-l-pentene; in other words the dimerization is accompanied only to a small degree by doubling of the initial dimer, methylpentene, which would lead to a C olefin.

The reason for such lack of further dimerization seems to be due to the absence of a reactive hydrogen atom on the secondary carbon atom of the double bond, which carbon atom is linked to a methyl group. On another hand it has been found that Z-methyl-l-pentene may add to propylene in the same conditions as those of its formation to yield a C olefin (nonene) which theoretically could by a similar addition be converted into a C olefin.

However such successive addition reactions are generally not sought for in the presence of alkyl-aluminium catalysts although the resulting compounds are valuable starting materials for chemical syntheses.

The principal reason therefor is that the formation of C and C olefins, as far as it can take place with acceptable yields, seriously complicates the recycling of the dimerization alkyl-aluminium catalyst which is made less active due to an increase of weight of the alkyl radicals bound to the aluminium atom.

On another hand it has also been suggested to dimerize a mixture of C and C olefins by heating said mixture with a catalyst consisting of a preformed complex of boron trifiuoride and an allcyl ether such as ethyl-ether in the presence of an excess of boron trifiuoride, the ratio of said complex with respect of the mixture of C and C olefins being about 4 to 6% by weight. The use of such a complex as a catalyst derives from experiments made concerning the unfavorable action of certain other catalysts, among which is boron fluoride alone, on the dimerization of C C olefins, in the usual proportions of about 4 percent by weight of the intial olefins. Using the said boron trifluoride alone in such a ratio leads to some dimerization of the said 'olefins but also, simultaneously to the production or" various trimers, tetramers, etc. in quantities which are so large that the yield of dimers loses all commercial interest.

One object of this invention is to provide for the manfacture of the sole C dimer of Z-methyl-l-pentene using the said Z-methyl-l-pentene as starting material, without any undesirable by-product.

Another object is to convert Z-methyH- entene into a C dimer with the use of boron trifluoride as the only catalyst, without the above mentioned complex.

Said objects are achieved by heating Z-methyl-l-pentenc at a temperature of about 45 to 180 C. and preferably from 55 to 170 C. in the presence of a quantity of boron trifluoride comprised between 0.5 and 5 parts per thousand, and preferably not higher than 2 parts per thousand, by weight of the initial olefin, while taking the necessary steps tc remove the reaction heat.

Polymerization is obtained in about 6 to 12 hours. The reaction may take place continuously or batchwise.

The limitation of the quantity of boron. trifluoride which is used is the basic feature of the invention. Any excess of said catalyst above the upper limit of. 5 parts per thousand, by weight, leads to a considerable increase of the proportion of undesirable proportions of higher polymers in the final product.

. It has furthermore been found that in order to insure a selective character to the reacton it is compulsory to remove immediately the heat evolved during the reaction. This does not imply the necessity of operating batchwise at constant temperature but it does require the avoiding of any uncontrolled rise of the temperature in the reaction medium. a

The mechanism of the dimerization has not been actually elucidated, a shifting of the double bond, with simultaneous formation of a mobile hydrogen atom may take place prior to said dimerization, in which case such a previous modification would be a result of the action of the boron trifluoride. The invention should however not be considered as being bound to the: more or less complex nature of the implied reactions.

The examples hereafter illustrate the process which should preferably be followed and the yields obtained according to the invention.

The apparatus used in the examples comprised a flask of 2 liters capacity provided with a glass ring column 40 cm. long and with a reflux cooler.

After making sure that the appartuswas completely dry, 1000 g. of 2 methyl-l-pentene were placed in the flask. According to the examples, 275 to 500 cc. of gaseous boron trifluoride were then fed to the flask.

The mixture was left to rest for four hours, then the flask was heated and the contents thereof maintained at boiling temperature under complete reflux. In said process the refluxing of methyl-pentane provided for the removal of the heat of reaction, more particularly at the beginning of the operation. The interior temperature in the flask slowly rose, which provided an index for the determination of the degree of dimerization. As soon as the temperature reached to C., according to the case, heating was interrupted and the reaction product was distilled under a pressure of 13 mm. Hg.

Tables I and II hereafter sum up the reaction condition in the various tests which were made and the result obtained. In Table II polymers is intended to mean undesirable trimers, tetramers and the higher polymers.

TABLE I Operating conditions BF; used 2-methyl-1- Heating Final tem- Exarn- Form of pentenc time, perature of ple No BF; used, g. hours flask, 0.

1 Gas 275 0. 8 1, 000 15 160 2 -.do 500 1.45 1, 000 10 155 3 do 500 1. 45 1,000 i 10 160 4- -d0 500 1. 45 l, 000 6 155 TABLE II Results Unconverted Dimer Polymers 2-n1ethyl-1- obtained formed Yield of Example pentene dimers, No. percent G. Percent G. Percent G. Percent 74 7. 4 836 83. G 90 9. 0 90. 3 90 9. O 808 80. 8 102 10. 2 8S. 8 70 7. 0 852 .85. 2 78 7.8 91. 7 78 7. 8 846 84. 6 76 7. 6 91. 8

a, a After rectifying the reaction mixture in an appropriate column, the fundamental characteristics of the dimer obtained according to the invention were the followlng.

Boiling zone 79-84 C. at 13 mm Hg. Molecular weight 168. -C=C groupings:

p. kg. 6.04.

A continuous operation is very advantageous because it permits recycling part of the products which are being converted. Under such conditions of operation it has been possible to reduce the proportions of polymers containing more than 12 carbon atoms to less than 3 percent by weight of the initial methylpentene, provided a convenient device was used for removing the heat of reaction.

The C olefin obtained according to the invention is not a pure substance but the boiling curve thereof is much flatter than that of the C olefins obtained when polymerizing propylene by the usual methods, i.e. of products which are generally named tetrapropylenes. The appended drawing shows the boiling curve obtained at 760 mm. Hg according to the ASTM standard test for a C olefin obtained according to the invention (full line) and a commercial tetrapropylene (dotted line), respectively.

Chromatographic analysis confirms the said indication. Of ten or so isomers possible in the dimer of Z-methyl-lpentene, eight are present in small quantities only and two apparently form the majority, whereas in tetrapropylene fifteen or so polymers may be found, about ten of which are present in quantities of the same order.

The decrease in height of the boiling zone makes it possible, as checked by corresponding tests, to obtain purer x0 aldehydes and alcohols when the methylpentene dimer is used rather than the usual tetrapropylene. The alcohols obtained through oxonization (i.e. hydr-oformylation followed by hydrogenation if desired) have a boiling point which is distinctly higher than that of the individual starting olefins or of the paraifins resulting from parasitical hydrogenation. However, if the boiling zone of the alcohols is too wide, the boiling point of the lighter alcohols may get undesirably near to that of the less volatile olefins or parafiins. This is the reason why the methylpentene dimer prepared according to the invention and having a narrow boiling interval is particularly adapted to the obtention of oxo alcohols having a high degree of purity. The same occurs with aldehydes.

The oxonization of the said dimer is conducted without difliculties and the yield thereof is higher than those observed with the usual tetramers. Furthermore the conversion of Z-methyl-pentene dimer to alkylbenzene may be operated in very good conditions and with high yields.

The alcohols resulting from the dimer of Z-methyl-lpentene may be converted by known processes either into plasticizing esters (through esterification by means of an acid) or into detergents or surface-active compounds.

In the latter case one or more mols of ethylene oxide per mol of alcohol may be bound to an oxo alcohol obtained according to the invention, thereafter the resulting compound is reacted with a sulfonating agent such as oleum, chlorosulfonic acid or sulfuric anhydride. Alkylsulfonic acids may thus be obtained with a high yield, which may thereafter be neutralized by means of ammonia, sodium hydroxide, ethanolamine or the like, or mixtures thereof.

The resulting salts are surface-active and have a foaming and wetting action which is better than that of the corresponding laurylsulfates. Said surface active properties are even as a Whole equal or superior to those of the alkylsulfates deriving from alcohols obtained through oxonization of tetrapropylene.

TABLE 111 Natural 0x0 alcohol 0x0 alcohol lauric derived from derived from alcohol tetra- 2-methylpropylene pentene dimer Moles of ethylene oxide per mole of alcohol (optimum) 2 3 3 Wetting action 1 Concentration, g./liter:

108 0.78 45 24 20 Foaming action 2 in hard Water (17 DH) concentration 0.78 gJliter: Time in minutes:

0 920 935 1, 000 700 660 710 650 600 625 Detergent tests: 3

(a) Reflectance concentration: 2.5 g./l 29 34 5 g./l 32 34 41 (10) Percent degreasing 42 42 60 1 Time of fall of cotton disk, seconds.

2 Volume of foam in cc. 7

3 Percent reflectance of a typical fabric, soiled, then cleaned with a detergent solution (launderometer).

Likewise, detergents obtained by converting the dimer of Z-methylpentene into alkylbenzene, sulfonating the resulting aralkyl compound and neutralizing the obtained acid by means of sodium hydroxide, ammonia or organic bases have remarkable uses.

As maybe seen the compounds obtained when starting from Z-methylpentene which is dimerized by means of boron fluoride in the above mentioned conditions have outstanding qualities which are inherent to the structure of the C olefin thus obtained.

We claim:

1. A process of dimerizing Z-methyl-l-pentene which comprises the steps of admixing liquid Z-methyl-l-pentene, as sole monomer, with a catalyst system consisting of 0.5 to 5 parts of boron trifluoride per thousand parts of said Z-methyl-l-pentene by weight, at a temperature between 45 C. and 180 C., rapidly, in the absence of oxygen, removing the heat of reaction evolved, and recovering a mixture of isomers of dimeric Z-rnethyl-lpentene substantially free of higher molecular weight polymers.

2. A process of dimerizing Z-methyl-l-pentene which comprises the steps of admixing liquid Z-methyl-l-pentene, as sole monomer, with a catalyst system consisting of 0.5 to 5 parts of boron trifluoride per thousand parts of said Z-methyl-l-pentene by weight, at a temperature between 55 C. and C., rapidly, in the absence of oxygen, removing the heat of reaction evolved, and recovering a mixture of isomers of dimeric 2-methyl-l-pentene substantially free of higher molecular weight polymers.

3. A process of dimerizing 2-methyl-1-pentene which comprises the steps of admixing liquid Z-methyl-l-pentene, as sole monomer, with a catalyst system consisting of 0.5 to 2 parts of boron trifiuoride per thousand parts of said 2-methyl-1-pentene by Weight, at a temperature between 45 C. and C., rapidly, in the absence of oxygen, removing the heat of reaction evolved, and recovering a mixture of isomers of diemric 2-methyl-1-pentene substantially free of higher molecular weight polymers.

4. A process of dimerizing Z-methyl-l-pentene which comprises the steps of admixing liquid Z-methyl-l-pentene, as sole monomer, with a catalyst system consisting of 0.5 to 2 parts of boron trifluoride per thousand parts of said 2-methy1-1-pentene by weight, at a temperature between 55 C. and 170 C., rapidly, in the absence of oxygen, removing the heat of reaction evolved, and recovering a mixture of isomers of dimeric 2-methyl-1- pentene substantially free of higher molecular weight polymers.

5. A process of dimerizing 2-methyl-1-pentene which comprises the steps of admixing liquid Z-methyl-l-pentene, as sole monomer, with a catalyst system consisting of 0.5 to 5 parts of boron trifluoride per thousand parts of said 2-methy1-1-pentene by weight, heating said ad mixture to reflux, rapidly removing the heat of reaction evolved by refluxing said admixture until the temperature of the reaction mass reaches 155 C. to 160 C., and recovering a mixture of isomers of dimeric 2-methy1-1- pentene substantially free of higher molecular weight polymers.

References Cited by the Examiner UNITED STATES PATENTS 2,181,640 11/39 Deanesly et al 260-685.15 2,221,000 11/40 Kuentzel et a1 260-683.15 2,315,080 3/43 Reid 260-683.15 2,421,946 6/47 Ipatiefi" 260-683.15 2,552,508 5/51 Peters 260-68315 2,806,072 9/57 Cohen et a1. 260-68315 2,976,338 3/61 Thomas 260-68315 3,009,972 11/61 Johnson 260-683.15

OTHER REFERENCES Doss: Physical Constants of the Principal Hydrocarbons, 4th edition, published by the Texas Company, New York (1943), pages 37-39 relied on.

ALPHONSO D. SULLIVAN, Primary Examiner. PAUL M. COUGHLAN, Examiner. 

1. A PROCESS OF DIMERIZING 2-METHYL-1-PENTENE WHICH COMPRISES THE STEPS OF ADMIXING LIQUID 2-METHYL-1-PENTENE, AS SOLE MONOMER, WITH A CATALYST SYSTEM CONSISTING OF 0.5 TO 5 PARTS OF BORON TRIFLUORIDE PER THOUSAND PARTS OF SAID 2-METHYL-1-PENTENE BY WEIGHT, AT A TEMPERATURE BETWEEN 45*C. AND 180*C., RAPIDLY, IN THE ABSENCE OF OXYGEN, REMOVING THE HEAT OF REACTION EVOLVED, AND RECOVERING A MIXTURE OF ISOMERS OF DIMERIC 2-METHYL-1- 